British researchers placed a harmless type of bacteria on the hands of volunteers in order to simulate poorly washed hands. They then had them use warm-air dryers, high-powered "jet-air" dryers or paper towels to dry their hands.

The investigators measured airborne bacteria levels and found higher amounts of germs around both types of dryers than around towel dispensers.

Jet-air dryers were the worst, the study found. Bacteria levels in the air around jet-air dryers were 4.5 times higher than around warm air dryers and 27 times higher than around paper towel dispensers, said a team led by Mark Wilcox of the University of Leeds.

His team also found that the bacteria persisted in the air around hand dryers long after they were used. Forty-eight percent of the bacteria around hand dryers was collected more than five minutes after use, and the bacteria could still be detected 15 minutes after use.

"Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it. You may also be splattered with bugs from other people's hands," Wilcox said in a university news release.

"These findings are important for understanding the ways in which bacteria spread, with the potential to transmit illness and disease," he added.

The study was published Nov. 20 in the Journal of Hospital Infection and was also presented at the Healthcare Infection Society International Conference in Lyon, France.